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SHORT COMMUNICATION

Denitrification Potential in Urban Riparian Zones

Institute of Ecosystem Studies, Box AB, Millbrook, NY 12545. Received 20 June 2002. *Corresponding author Published in J. Environ. Qual. 32:1144–1149 (2003)

groffmanp{at}ecostudies.org

	ABSTRACT

TOP ABSTRACT INTRODUCTION Materials and Methods Results Discussion REFERENCES

 
Denitrification, the anaerobic microbial conversion of nitrate to nitrogen (N) gases, is an important process contributing to the ability of riparian zones to function as "sinks" for NO^-₃ in watersheds. There has been little analysis of riparian zones in urban watersheds despite concerns about high NO^-₃ concentrations in many urban streams. Vegetation and soils in urban ecosystems are often highly disturbed, and few studies have examined microbial processes like denitrification in these ecosystems. In this study, we measured denitrification potential and a suite of related microbial parameters (microbial biomass carbon [C] and N content, potential net N mineralization and nitrification, soil inorganic N pools) in four rural and four urban riparian zones in the Baltimore, MD metropolitan area. Two of the riparian zones were forested and two had herbaceous vegetation in each land use context. There were few differences between urban and rural and herbaceous and forest riparian zones, but variability was much higher in urban than rural sites. There were strong positive relationships between soil moisture and organic matter content and denitrification potential. Given the importance of surface runoff in urban watersheds, the high denitrification potential of the surface soils that we observed suggests that if surface runoff can be channeled through areas with high denitrification potential (e.g., stormwater detention basins with wetland vegetation), these areas could function as important NO^-₃ sinks in urban watersheds.

	INTRODUCTION

TOP ABSTRACT INTRODUCTION Materials and Methods Results Discussion REFERENCES

 
DENITRIFICATION, THE ANAEROBIC MICROBIAL conversion of NO^-₃ to N gases (NO, N₂O, N₂), is an important component of the water quality maintenance value of riparian ecosystems. These ecosystems have been shown to prevent the movement of upland-derived nitrate (NO^-₃) into streams in many areas (Gilliam, 1994; Hill, 1996). Nitrate is the most common drinking water pollutant in U.S. ground waters (USEPA, 1990) and causes eutrophication in coastal and marine waters (Diaz, 2001). Riparian zones have been proposed to help solve eutrophication problems in watersheds around the world (Lowrance et al., 1997; Gren et al., 1997; Mitsch et al., 2001). Denitrification is important in these ecosystems because it removes N from the ecosystem, converting it to gas, while other mechanisms of NO^-₃ removal (plant uptake, microbial immobilization) leave N in the ecosystem, potentially leading to N saturation and loss at a later time (Aber et al., 1989; Hanson et al., 1994).

The vast majority of riparian denitrification research has been in agricultural and forested watersheds. There have been few studies of denitrification in soils in urban areas despite the fact that urban watersheds commonly deliver high loads of NO^-₃ to coastal waters (Miller et al., 1997). In general, the biological capacity of urban soils is poorly characterized relative to agricultural and forest soils due to the highly variable and disturbed nature of urban parent materials and environmental conditions (DeKimpe and Morel, 2000; Pouyat et al., 2002). Urban watersheds also have highly altered hydrology, with increased amounts of water moving toward streams as surface runoff and reduced amounts of infiltration to ground water (Dunne and Leopold, 1978; Rose and Peters, 2001). Although this alteration of runoff and ground water flow paths has the potential to reduce the ability of riparian zones to intercept and remove upland-derived NO^-₃ (Gold et al., 2001), urban watersheds often contain significant amounts of undeveloped riparian zones as well as other areas with potential for biogeochemical processing of upland-derived nutrients (e.g., stormwater detention basins, floodplains, drainage swales, roadside ditches). Given societal pressure to reduce NO^-₃ delivery from urban watersheds to coastal waters (Boesch et al., 2001), there is a need to determine if urban riparian zones and other urban areas with potential functional importance support rates of denitrification similar to those observed in agricultural and forested watersheds.

In this paper we present measurements of denitrification potential in riparian zones in and around the city of Baltimore, MD. The work is part of the Baltimore Ecosystem Study (BES), a new component of the U.S. National Science Foundation's Long Term Ecological Research (LTER) network (http://www.beslter.org; verified 31 Dec. 2002). We measured denitrification enzyme activity (potential) and a series of ancillary variables in four urban and four rural–suburban riparian sites with forest or herbaceous vegetation cover. Our objectives were to (i) evaluate the effects of vegetation cover and land use setting on denitrification potential in urban riparian zones and (ii) evaluate basic soil controls (water content, organic matter) on denitrification potential in urban riparian soils.

	Materials and Methods

TOP ABSTRACT INTRODUCTION Materials and Methods Results Discussion REFERENCES

 
Sampling Sites
We sampled eight riparian sites with either herbaceous or forest cover. Two herbaceous and two forest sites were located in the rural–suburban portion of the Baltimore metropolitan area (76°30' W, 39°15' N) and two herbaceous and two forest sites were in the urban core of the city.

At one rural location, the herbaceous and forest sites were located within 10 m of each other along the same stream. These two sites were in a nearly 100% forested watershed where the herbaceous site was created by forest cutting for a power line that crosses the stream, creating an approximately 50-m-wide herbaceous swath through the forested watershed. Thus, the area above the herbaceous riparian zone was herbaceous and the area above the forested riparian zone was forested. The stream at this site has very low (<1.0 mg N L^-1) NO^-₃ concentrations (Groffman et al., 2002).

At the second rural location, the herbaceous and forest sites were located within 100 m of each other, but along different streams. Upland land use at this location was an agricultural (maize, Zea mays L.) field. The herbaceous area was approximately 30 m wide and the forested area was approximately 100 m wide. A nearby stream draining a small agricultural watershed has NO^-₃ concentrations greater than 4.0 mg N L^-1 (Groffman, unpublished data, 2002).

The urban sites were located on city-owned park land, were separated by 1 to 5 km along the same stream, and were approximately 30 km closer to the urban core of Baltimore than the rural sites. Stream NO^-₃ concentrations were between 1 and 2 mg N L^-1 (Groffman et al., 2002). The grass sites were located on a floodplain that had been mowed within the past 5 to 10 yr. Upland land use for both the herbaceous and forest sites was a mixture of residential and forested and grass park areas.

Soils at the rural location where the forest and herbaceous sites were within 10 m of each other were classified as fine-loamy, mixed, mesic Aquic Fragiudults (Groffman et al., 2002). At other locations, soils were disturbed and variable, as is common in urban (Pouyat et al., 2002) and riparian (Rosenblatt et al., 2001) areas. Overstory vegetation in the forested riparian areas was dominated by red maple (Acer rubrum L.), ash (Fraxinus pennsylvanica Marsh.), elm (Ulmus americana L.), birch (Betula nigra L.), and sycamore (Platanus occidentalis L.). Vegetation in the herbaceous sites was variable ranging from a mixture of sedges (Carex spp.) and cattails (Typha spp.) in the rural sites to upland grasses (Festuca spp., Poa spp., Lolium spp.) at one urban site and nearly complete dominance by common reed (Phragmites spp.) in the other. Average annual precipitation in the area is approximately 1090 mm yr^-1 and stream discharge is approximately 380 mm yr^-1 (Froelich et al., 1980).

Analytical Methods
Soil samples (three replicates at six of the sites, two replicates at two of the sites) were taken in June 1998 with a "bulb corer" sampling tool to a depth of 10 cm and were placed in plastic bags. At all sites, samples were taken 5 m from the stream bank to control for differences in stream size and riparian zone width among sites.

Samples were stored at 4°C between sampling and analysis (less than one week). Soil samples were hand sorted and mixed and held at field moisture for all analyses. Soil moisture content was determined by drying at 60°C for 48 h (McInnes et al., 1994). Soil organic matter content was determined by loss on ignition at 450°C for 4 h (Nelson and Sommers, 1996). Amounts of inorganic N (NO^-₃ and NH⁺₄) in soil were determined by extraction with 2 M KCl followed by colorimetric analysis with a flow solution analyzer (Perstorp AB, Perstorp, Sweden).

Denitrification enzyme activity (DEA) was measured with the short-term anaerobic assay developed by Smith and Tiedje (1979) as described by Groffman et al. (1999). Sieved soils were amended with NO^-₃, dextrose, chloramphenicol, and acetylene, and were incubated under anaerobic conditions for 90 min. Gas samples were taken at 30 and 90 min, stored in evacuated glass tubes, and analyzed for N₂O by electron capture gas chromatography.

Microbial biomass C and N content was measured with the chloroform fumigation–incubation method (Jenkinson and Powlson, 1976). Soils were fumigated to kill and lyse microbial cells in the sample. The fumigated sample was inoculated with fresh soil, and microorganisms from the fresh soil grew vigorously using the killed cells as substrate. The flushes of carbon dioxide (CO₂) and 2 M KCl extractable inorganic N (NH⁺₄ and NO^-₃) released by the actively growing cells during a 10-d incubation at field moisture content were assumed to be directly proportional to the amount of C and N in the microbial biomass of the original sample. A proportionality constant (0.45) was used to calculate biomass C from the CO₂ flush. Carbon dioxide was measured by thermal conductivity gas chromatography. Inorganic N flush data were not corrected with a proportionality constant.

Inorganic N and CO₂ production were also measured in unfumigated "control" samples. These incubations provided estimates of soil respiration and potential net N mineralization and nitrification. Soil respiration was quantified from the amount of CO₂ evolved over the 10-d incubation. Potential net N mineralization and nitrification were quantified from the accumulation of NH⁺₄ plus NO^-₃ and NO^-₃ alone during the 10-d incubation. Ammonium and NO^-₃ were measured as described above.

Statistical Analysis
Land use setting (urban versus rural–suburban) and vegetation type (herbaceous versus forested) were compared with two-way analysis of variance, with interactions. Relationships between variables were evaluated with correlation and regression analysis. The SAS statistical program was used for all analyses (SAS Institute, 1988).

	Results

TOP ABSTRACT INTRODUCTION Materials and Methods Results Discussion REFERENCES

 
In the eight sites sampled, DEA ranged from 0.23 to 7.59 mg N kg^-1 h^-1, with more variation among the urban than rural sites (Fig. 1) . There were no significant differences in DEA between urban versus rural, or between forested versus herbaceous sites (Table 1) and there were no significant interactions between land use and vegetation effects. There were strong relationships between DEA and soil moisture (r² = 0.55, p < 0.0001) and soil organic matter (r² = 0.68, p < 0.0001) content (Fig. 2) . Soil moisture and organic matter content were highly correlated (r² = 0.56, p < 0.0001). These relationships between DEA, soil moisture, and organic matter content were probably the cause of the higher variability in DEA among the urban sites. Two of the urban sites were quite dry, with low organic matter content, and one was very wet and organic rich.

View larger version (12K): [in this window] [in a new window]   Fig. 1. Denitrification enzyme activity in soils (0–10 cm) from four urban and four rural riparian sites in the Baltimore metropolitan area, June 1998. Two of the sites in each land use class had forested vegetation cover and two had herbaceous vegetation cover.

View larger version (16K): [in this window] [in a new window]   Fig. 2. Denitrification enzyme activity in soils (0–10 cm) from eight riparian sites from urban or rural land use settings with forested or herbaceous vegetation cover versus soil moisture (top panel) and soil organic matter (bottom panel).

	Discussion

TOP ABSTRACT INTRODUCTION Materials and Methods Results Discussion REFERENCES

 
Our data show that urban conditions do not lead to inherently low denitrification potential in riparian zones. The lack of difference in denitrification potential between urban and rural sites suggests that an urban land use context does not necessarily reduce the biological NO^-₃ sink potential of urban riparian zones. It is important to note that most of the urban sites were highly altered from their natural state, with large amounts of trash, physical disturbance of the soil, and exotic plant species. Our data show, however, that as long as these sites are wet, with high levels of soil organic matter, they will have high denitrification potential. Strong control of denitrification potential by water and organic matter content is consistent with many previous studies (Groffman, 1994; Hunter and Faulkner, 2001; Clement et al., 2002).

The lack of difference in denitrification potential between forested and herbaceous riparian sites is important for assessing and managing riparian NO^-₃ sinks in urban areas. There has been extensive uncertainty in the riparian literature about the importance of maintaining forest vegetation in riparian zones (Haycock and Pinay, 1993; Lowrance et al., 1995; Schnabel et al., 1996; Addy et al., 1999; Clement et al., 2002). The vegetation comparison was especially illustrative at the site where the forested and herbaceous sites were less than 10 m apart. These sites were in a nearly 100% forested county park, with the herbaceous site a product of forest removal for maintenance of a power line that cuts across the park. Denitrification potential was very similar at these sites (4.16 in the forest versus 4.14 mg N kg^-1 h^-1 in the herbaceous). Our results suggest that there can be some flexibility in vegetation management in urban riparian zones, at least with respect to denitrification function, as long as this management maintains high levels of soil moisture and organic matter.

The highest denitrification potential (7.60 mg N kg^-1 h^-1) and microbial biomass (968 mg C kg^-1) that we observed were in an urban common reed (Phragmites spp.) stand that developed near the outlet of a broken storm drain that empties onto a highly disturbed flood plain. These results are consistent with previous studies showing that common reed alters N cycling in wetland soils and supports high levels of denitrification potential (Templer et al., 1998; Otto et al., 1999; Windham, 2001). Highly disturbed sites dominated by common reed and other weedy wetland vegetation (e.g., Typha spp., Lythrum spp.) are often found in urban watersheds. Our results show that these typical urban sites have some functional value that could be exploited in urban watershed management or restoration efforts.

The fact that there were higher correlations between denitrification potential and C cycle–related variables (microbial biomass C, respiration) than with N cycle–related variables (microbial biomass N, potential net N mineralization and nitrification, inorganic N pools) suggests that organic matter accumulation and soil C dynamics are critical controllers of variation in denitrification potential in these urban sites. These results are somewhat surprising because variation in denitrification potential is frequently found to be highly influenced by N richness, or NO^-₃ loading (Groffman, 1994; Ettema et al., 1999; Lowrance and Hubbard, 2001). There are some distinctive controls on soil carbon dynamics in urban ecosystems, ranging from air pollution–induced changes in litter quality to dramatic alterations of soil fauna (Groffman et al., 1995; Pouyat et al., 2002). These controls need to be considered in management of urban riparian zone denitrification. Given the active geomorphology of urban streams, with periods of extensive erosion and deposition, it may be challenging to assess and manage C levels in urban riparian zones (Pouyat et al., 2002).

It is important to note that while we are reporting measurements of surface soil denitrification potential, the vast majority of riparian denitrification work has focused on ground water NO^-₃ and subsurface denitrification (Hill, 1996). The focus on subsurface denitrification is logical in agricultural and forested watersheds, where the majority of NO^-₃ transport from uplands to streams is in ground water. However, in urban watersheds, infiltration to ground water is greatly reduced by the presence of impervious surfaces, and surface runoff is frequently channeled directly to the stream through engineered storm drainage systems.

Given the importance of surface runoff in urban watersheds, the high denitrification potential of the surface soils that we observed has implications for restoration and management of riparian NO^-₃ removal functions in urban watersheds. If surface runoff can be channeled through areas with high denitrification potential (e.g., stormwater detention basins with weedy wetland vegetation), NO^-₃ delivery to urban streams could be reduced (Casey et al., 2001). While the focus of most stormwater management efforts is sediment control, our results suggest that if we manage the vegetation and soil C levels in stormwater control structures, we may be able to restore and/or create important NO^-₃ sinks in urban watersheds.

	ACKNOWLEDGMENTS

 
We thank Alan Lorefice and Emilie Stander for help with laboratory analysis. This paper is a contribution to the Baltimore Ecosystem Study and the Institute of Ecosystem Studies and was funded by National Science Foundation grant DEB 97-14835.

	REFERENCES

TOP ABSTRACT INTRODUCTION Materials and Methods Results Discussion REFERENCES

 

• Aber, J.D., K.J. Nadelhoffer, P. Steudler, and J.M. Melillo. 1989. Nitrogen saturation in northern forest ecosystems. Bioscience 39:378–386.[ISI]
• Addy, K.L., A.J. Gold, P.M. Groffman, and P.A. Jacinthe. 1999. Ground water nitrate removal in subsoil of forested and mowed riparian buffer zones. J. Environ. Qual. 28:962–970.[Abstract/Free Full Text]
• Boesch, D.F., R.B. Brinsfield, and R.E. Magnien. 2001. Chesapeake Bay eutrophication: Scientific understanding, ecosystem restoration, and challenges for agriculture. J. Environ. Qual. 30:303–320.[Abstract/Free Full Text]
• Casey, R.E., M.D. Taylor, and S.J. Klaine. 2001. Mechanisms of nutrient attenuation in a subsurface flow riparian wetland. J. Environ. Qual. 30:1732–1737.[Abstract/Free Full Text]
• Clement, J.C., G. Pinay, and P. Marmonier. 2002. Seasonal dynamics of denitrification along hydrotoposequences in three different riparian wetlands. J. Environ. Qual. 31:1025–1037.[Abstract/Free Full Text]
• DeKimpe, C.R., and J.L. Morel. 2000. Urban soil management: A growing concern. Soil Sci. 165:31–40.
• Diaz, R.J. 2001. Overview of hypoxia around the world. J. Environ. Qual. 30:275–281.[Abstract/Free Full Text]
• Dunne, T., and L.B. Leopold. 1978. Water in environmental planning. W.H. Freeman, New York.
• Ettema, C.H., R. Lowrance, and D.C. Coleman. 1999. Riparian soil response to surface nitrogen input: Temporal changes in denitrification, labile and microbial C and N pools, and bacterial and fungal respiration. Soil Biol. Biochem. 31:1609–1624.
• Froelich, A.J., J.T. Hack, and E.G. Otton. 1980. Geologic and hydrologic map reports for land-use planning in the Baltimore-Washington urban area. Circ. 806. U.S. Geol. Survey, Reston, VA.
• Gilliam, J.W. 1994. Riparian wetlands and water quality. J. Environ. Qual. 25:896–900.
• Gold, A.J., P.M. Groffman, K. Addy, D.Q. Kellogg, M. Stolt, and A.E. Rosenblatt. 2001. Landscape attributes as controls on groundwater nitrate removal capacity of riparian zones. J. Am. Water Resour. Assoc. 37:1457–1464.
• Gren, I.M., T. Soderqvist, and F. Wulff. 1997. Nutrient reductions to the Baltic Sea: Ecology, costs and benefits. J. Environ. Manage. 51:123–143.
• Groffman, P.M. 1994. Denitrification in freshwater wetlands. Curr. Top. Wetland Biogeochem. 1:15–35.
• Groffman, P.M., N.J. Boulware, W.C. Zipperer, R.V. Pouyat, L.E. Band, and M.F. Colosimo. 2002. Soil nitrogen cycle processes in urban riparian zones. Environ. Sci. Technol. 36:4547–4552.[Medline]
• Groffman, P.M., E. Holland, D.D. Myrold, G.P. Robertson, and X. Zou. 1999. Denitrification. p. 272–288. In G.P. Robertson, C.S. Bledsoe, D.C. Coleman, and P. Sollins (ed.) Standard soil methods for long term ecological research. Oxford Univ. Press, New York.
• Groffman, P.M., R.V. Pouyat, M.J. McDonnell, S.T.A. Pickett, and W.C. Zipperer. 1995. Carbon pools and trace gas fluxes in urban forest soils. p. 147–158. In R. Lal, J. Kimble, E. Levine, and B.A. Stewart (ed.) Advances in soil science: Soil management and greenhouse effect. CRC Press, Boca Raton, FL.
• Hanson, G.C., P.M. Groffman, and A.J. Gold. 1994. Symptoms of nitrogen saturation in a riparian wetland. Ecol. Appl. 4:750–756.
• Haycock, N.E., and G. Pinay. 1993. Groundwater nitrate dynamics in grass and poplar vegetated riparian buffer strips during the winter. J. Environ. Qual. 22:273–278.[Abstract/Free Full Text]
• Hill, A.R. 1996. Nitrate removal in stream riparian zones. J. Environ. Qual. 25:743–755.[Abstract/Free Full Text]
• Hunter, R.G., and S.P. Faulkner. 2001. Denitrification potentials in restored and natural bottomland hardwood wetlands. Soil Sci. Soc. Am. J. 65:1865–1872.[Abstract/Free Full Text]
• Jenkinson, D.S., and D.S. Powlson. 1976. The effects of biocidal treatments on metabolism in soil V. A method for measuring soil biomass. Soil Biol. Biochem. 8:209–213.
• Lowrance, R., L.S. Altier, J.D. Newbold, R.R. Schnabel, P.M. Groffman, J.M. Denver, D.L. Correll, J.W. Gilliam, J.L. Robinson, R.B. Brinsfield, K.W. Staver, W. Lucas, and A.H. Todd. 1997. Water quality functions of riparian forest buffers in Chesapeake Bay watersheds. Environ. Manage. 21:687–712.[Medline]
• Lowrance, R., and R.K. Hubbard. 2001. Denitrification from a swine lagoon overland treatment system at a pasture–riparian zone interface. J. Environ. Qual. 30:617–624.[Abstract/Free Full Text]
• Lowrance, R., G. Vellidis, and R.K. Hubbard. 1995. Denitrification in a restored riparian forest wetland. J. Environ. Qual. 24:808–815.[Abstract/Free Full Text]
• McInnes, K.J., R.W. Weaver, and M.J. Savage. 1994. Soil water potential. p. 53–58. In R.W. Weaver (ed.) Methods of soil analysis. Part 2. Microbiological and biochemical properties. SSSA, Madison, WI.
• Miller, C.V., J.M. Denis, S.W. Ator, and J.W. Barkebill. 1997. Nutrients in streams during baseflow in selected environmental settings of the Potomac River basin. J. Am. Water Resour. Assoc. 33:1155–1171.
• Mitsch, W.J., J.W. Day, Jr., J.W. Gilliam, P.M. Groffman, D.L. Hey, G.W. Randall, and N. Wang. 2001. Reducing nitrogen loading to the Gulf of Mexico from the Mississippi River basin: Strategies to counter a persistent ecological problem. Bioscience 51:373–388.[ISI]
• Nelson, D.W., and L.E. Sommers. 1996. Total carbon, organic carbon, and organic matter. p. 961–1010. In D.L. Sparks (ed.) Methods of soil analysis. Part 3. Chemical methods. SSSA, Madison, WI.
• Otto, S., P.M. Groffman, S.E.G. Findlay, and A. Arreola. 1999. Invasive plant species and microbial processes in a tidal freshwater marsh. J. Environ. Qual. 28:1252–1257.[Abstract/Free Full Text]
• Pouyat, R., P. Groffman, I. Yesilonis, and L. Hernandez. 2002. Soil carbon pools and fluxes in urban ecosystems. Environ. Pollut. 116:107–188.
• Rose, S., and N.E. Peters. 2001. Effects of urbanization on streamflow in the Atlanta area (Georgia, USA): A comparative hydrological approach. Hydrol. Proc. 15:1441–1457.
• Rosenblatt, A.E., A.J. Gold, M.H. Stolt, and P.M. Groffman. 2001. Identifying riparian sinks for watershed nitrate using soil surveys. J. Environ. Qual. 30:1596–1604.[Abstract/Free Full Text]
• SAS Institute. 1988. SAS/STAT user's guide. Release 6.03. SAS Inst., Cary, NC.
• Schnabel, R.R., L.F. Cornish, W.L. Stout, and J.A. Shaffer. 1996. Denitrification in a grassed and a wooded, valley and ridge, riparian ecotone. J. Environ. Qual. 25:1230–1235.[Abstract/Free Full Text]
• Smith, M.S., and J.M. Tiedje. 1979. Phases of denitrification following oxygen depletion in soil. Soil Biol. Biochem. 11:262–267.
• Templer, P., S. Findlay, and C. Wigand. 1998. Sediment chemistry associated with native and non-native emergent macrophytes of a Hudson River marsh ecosystem. Wetlands 18:70–78.[ISI]
• USEPA. 1990. National pesticide survey: Nitrate. Office of Water, Office of Pesticides and Toxic Substances, Washington, DC.
• Windham, L. 2001. Comparison of biomass production and decomposition between Phragmites australis (common reed) and Spartina patens (salt hay grass) in brackish tidal marshes of New Jersey, USA. Wetlands 21:179–188.

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This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Related articles in JEQ Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (18) Citing Articles via Google Scholar Google Scholar Articles by Groffman, P. M. Articles by Crawford, M. K. Search for Related Content PubMed PubMed Citation Articles by Groffman, P. M. Articles by Crawford, M. K. GeoRef GeoRef Citation Agricola Articles by Groffman, P. M. Articles by Crawford, M. K. Related Collections Soil Microbiology Wetland Soils Biogeochemical Processes Nitrogen